On 10/16/2019 at 8:04 PM, HSL said:

Is it possible to buy the diaphragm anywhere? Have not been able to source it so far... 

Unlikely.  Not from Nissan anyway.

And not easy to get hold of a used bcdd in good condition, at least not found anything so far. Could just block it off of course but would like to have it, it's there for a reason..